1 76 PALEONTOLOGY OF NEW JEKSEY. 



It is even more than probable that the shells of this species, when per- 

 fect, have been gaping at the posterior, if not at each end; but all those 

 which I have seen have been more or less compressed and imperfect, so 

 that their closed character cannot be said to be certainly determined. As 

 they appear to possess all the features of the typical forms of the genus in 

 other respects, it would be safe to assume they have been somewhat gaping, 

 at least posteriorly. On the large specimen figured, which is the property 

 of the Am. Mus. of Nat. History, New York, the anterior muscular imprint 

 is seen to be of large size near the anterior end, but only faintly marked. 



Formation and localities, — The species is found at Monmouth, Burling- 

 ton, and other localities in the Lower Green Marls of New Jersey, and is 

 credited by Mr. Gabb to Delaware and to Mississippi. The original figure 

 given by Morton, he, cit, is very erroneous in all its details, having but little 

 resemblance to any specimen which I have ever seen. 



Pholadomya Roemeri n. sp. 

 Plate XXIV, Fig. 4. 



Shell rather small for the genus, being only about two inches long. 

 Valves very convex, with moderately tumid beaks, which are nearly termi- 

 nal ; form obHquely ovate in outline, somewhat wider behind the middle 

 than in front, exclusive of the beaks. Hinge-line rather long. Surface of 

 the shell marked by thirteen radiating ribs, which are sharp and elevated, 

 and are separated by broad concave interspaces. Those on the anterior 

 end of the shell are distant and curved forward, while those on the body of 

 the shell gradually decrease in distance as they progress backward. There 

 are also very distinct and proportionally distant concentric strise marking 

 the shell, forming slight nodes on the radii where crossing them. 



This species, so far as seen, is smaller than P. occidentalis Morton, and 

 is less regularly oval in outline, being more elongate. The radii are much 

 less numerous, in fact are less than half as numerous as is usual on that 

 species. It approaches much more nearly in form and character to P. peder- 

 nalis Romer, from Texas, but does not possess the prominent beaks of that 

 species, and has rather more radii, that one having only six or seven. 



